Fullerenes, Nanotubes and Carbon Nanostructures vol:13 pages:139-146
Helical carbon nanotubes were produced on silica-supported Co catalysts by chemical vapour decomposition of acetylene. Coiled nanotubes were examined. They have been found to be of various shapes, diameter, and pitch. Some of them are extremely long, up to 5 mu m, with regular helices. The average outer diameter of coils are about 30-50 nm, the pitch is in the range 50-200 nm and the length about 1- 1.4 mu m. The helix-shaped windings of the helical carbon nanotubes reveal characteristic mechanical resonances, which are determined by the elastic modulus, mass, shape, and dimensions.